The present invention relates to a vehicular headlamp of a type employing a semiconductor light-emitting device incorporating a plurality of light-emitting elements as a light source, and in which different illuminating functions with different beams can be achieved by selectively activating the various semiconductor light-emitting elements.
Most commonly, an incandescent bulb or a discharge bulb has conventionally been used as a light source of a vehicular headlamp. However, more recently semiconductor light-emitting elements such as light-emitting diodes (LEDs) have been employed in order to achieve lower electric power consumption and a more compact size.
Examples of lamps using LEDs include high-mount stop lamps, rear side marker lamps, and the like.
When semiconductor light-emitting elements such as LEDs are used as a light source of a vehicular headlamp, special optical design techniques are required in order to create a suitable light distribution pattern for a low-beam. For example, as disclosed in Japanese Patent Application Laid-Open No. 2001-266620 (FIGS. 1 and 4), in order to implement multiple optical functions, switching is carried out using a large number of semiconductor light sources arranged in a matrix configuration.
Since switching between a low beam and a high beam is necessary in a vehicular headlamp, in a headlamp employing a plurality of semiconductor light-emitting elements the light-emitting elements to be activated must be selected in accordance with the type of beam to be emitted. However, since conventionally known semiconductor light-emitting elements have not been designed taking into consideration the required light distribution patterns for a vehicle, there are various problems in optical design which occur when using such elements as a light source. For example, for a low-beam light distribution pattern it is difficult to clearly form a cut line (cut-off line) defining a contrast boundary. In addition, use of a large number of light-emitting elements causes a problem in that the total space occupied by the light-emitting elements is large.